(1) Field of the Invention
The present invention relates to the fabrication of integrated circuit devices, and more particularly, to a method of selective gate N-type and P-type electrodes using dual gate electrode deposition and patterning in the fabrication of integrated circuits.
(2) Description of the Prior Art
For 0.1 μm CMOS and below, poly gate depletion is one of the critical issues in achieving high performance devices. Polysilicon-germanium (PolySiGe) is an attractive gate material because of its lower gate depletion and boron penetration and better electron mobility. The main drawback with PolySiGe is the degradation of NMOS under the current CMOS process conditions. The germanium ion reduces overall N-dopant activation in the polygate structure causing degradation to the NMOS structure. It is desired to form NMOS and PMOS gates selectively where N type gates are formed without SiGe and P type gates are formed with SiGe.
U.S. Pat. Nos. 6,358,819 B1 to Shelton et al, 5,918,116 to Chittipeddi, and 6,063,670 B1 to Lin et al disclose dual gate oxide processes. U.S. Pat. No. 6,342,438 B2 to Yu et al teaches doping PMOS and NMOS regions differently before patterning polysilicon gates. U.S. Pat. No. 5,356,821 to Naruse et al disclose epitaxial growth of SiGe gates for both NMOS and PMOS. U.S. Pat. No. 6,376,323 B1 to Kim et al teaches PolySiGe gates for both PMOS and NMOS with selective doping. Co-pending U.S. patent application Ser. No. 10/266,425 (CS-01-093) filed on Oct. 8, 2002 discloses a method for forming SiGe gates having different Ge concentrations for PMOS and NMOS.